JPS5947733A - Plasma processing apparatus - Google Patents

Abstract

PURPOSE:To variably control in wide range parameters of plasma for plasma processing while a sample temperature is kept low, by providing an energy modulation means which modulates amplitude of energy to be supplied to a plasma generating means. CONSTITUTION:After a vacuum chamber consisting of a reaction chamber 1 and a discharge chamber 2 is exhausted, a discharge gas G is supplied to the vacuum chamber through a needle valve 3. A microwave is propagated through a waveguide 7 and is then sent to the inside of discharge tube 8. A power modulator 12 is connected between a microwave generator 6 and a power supply 11. A magnetic field is formed in a part of region within the discharge chamber 2 and reaction chamber 1 by an electromagnet 9 and a permanent magnet 10. When a microwave field is supplied to the discharge chamber 2 under such condition, the microwave discharge having magnetic field is generated and thereby plasma is formed. The active ion and neutral radical formed in such plasma are sent to the surface of sample 4 on the sample board 5 and etching is here carried out. The high density, high electron temperature plasma and low density, low electron temperature plasma are periodrically generated in the discharge chamber 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to improvement of a plasma processing apparatus for treating the surface of a sample using plasma. The present invention relates to a means for making it possible to vary and control the characteristics of a wide range of properties.

[Prior art]

FIG. 1 shows an example of the configuration of a conventional plasma processing apparatus, which is a magnetic field microwave plasma etching apparatus (J(, 5uzuki et at.

:JJAP 16 (1977) 1979). In the figure, after a vacuum chamber consisting of a reaction chamber and a discharge chamber 2 is evacuated to a vacuum (approximately IQ = 'l'orr) by an exhaust system 14, a discharge gas G is pumped through a needle pulp 3 to a predetermined pressure. (101~
10-I Torr) into the vacuum chamber.

Microwaves (frequency: 1 to 10GH2, usually 2.45G) generated by a microwave oscillator (usually a magnetron) 6
H2) propagates through the waveguide 7 and is introduced into the discharge tube 8 forming the discharge chamber 2. This discharge tube 8 is made of an insulator (usually quartz or alumina) to allow microwaves to pass through.

11 is a power source for operating the microwave oscillator 6; A magnetic field is formed in the discharge chamber 2 and a part of the reaction chamber 1 by the electromagnet 9 and the permanent magnet 10 . In this state, when an eshima f chromatic electric field is supplied to the microwave oscillator 6 in the discharge chamber 2, a magnetic field microwave discharge is generated due to the mutual interaction between the magnetic field and the microwave electric field, and a plasma is formed. Ru.

Active ions and neutral radicals formed in the plasma reach the surface of the sample 4 placed on the sample 5, and etching is performed. For example, when etching sample 4 made of an SI wafer with CF4 scum, CF4 molecules are decomposed in the plasma to form F", CFn" (n=
1 to 3), and F.

Neutral radicals such as CFn (n=1 to 3) enter the .111 surface of the Bi test stick 4 and react. As a result, the volatile % substance 5j
Etching is performed by forming F4 and stripping S1 atoms from the surface of the 8' sample 4. 5f02, which is commonly used as an insulating material for semiconductor devices, is similarly etched during the discharge of CF4 gas. However, the particles that contribute to Si etching are mainly F'', Fp, 5iOz
The particles that contribute to etching are mainly Cpn'' (11=l
~3).

In addition, when etching is performed using ions such as F'' and C@Fn'' (n=1 to 3), the etching is perpendicular to the surface of sample 4, as shown in Figure 2). As the etching progresses, etching is performed through the mask 15 (anisotropic etching). On the other hand, when etching is performed using neutral radicals such as F and CFn (n=1 to 3), the etching progresses in the same direction as shown in FIG. A side etching phenomenon occurs at the bottom (isotropic etching). That is, the cross-sectional shape of the etching differs depending on whether the particles to be etched are ions or neutral radicals, or the ratio of the two.

In the actual manufacturing process of semiconductor devices, (1) S
' A wide range of control over the etching rate ratio (selectivity) of the material to be etched, such as HS iOx, and (2) a wide range of control over the cross-sectional shape of the etching are desired. In order to carry out such control, it is necessary to control over a wide range the ratio of ions to neutral radicals formed in the plasma and incident on the surface of the sample 4, the ion species, and the neutral radical species. To control this, it is necessary to control over a wide range of plasma parameters (electron temperature and plasma density) that form ions and neutral radicals. In order to control this parameter, it is necessary to control the power used for plasma generation, for example, microwave power, over a wide range.

However, the temperature of sample 4 was lowered (below 100C).
Since it is practically desired to maintain the plasma power, there is a problem in that the plasma generation power cannot be sufficiently increased in conventional devices.

The above is about plasma etching equipment, but what about plasma deposition equipment? Similarly, in other plasma processing equipment such as #, it is desired to control the ratio of ions to neutral radicals, ion species, and neutral radical species over a wide range while keeping the sample temperature low. .

[Purpose of the invention]

Accordingly, an object of the present invention is to provide a plasma processing apparatus that allows the parameters of plasma for plasma processing to be variably controlled over a wide range while keeping the sample temperature low.

[Summary of the invention]

In order to achieve the above object, the present invention includes a gas introducing means for introducing a discharge gas into a vacuum chamber, a plasma forming means for forming a plasma of the discharge gas in the vacuum chamber, and a plasma forming means for forming a discharge gas plasma in the vacuum chamber. A sample stage on which a sample to be surface-treated is placed by injecting particles, and energy supplied to the plasma forming means so that the plasma periodically forms a strong plasma state, a weak plasma state, and a plasma extinction state. The plasma processing apparatus e is characterized by an energy modulation means for modulating the size and a trap.

The characteristic configuration 1cj of the present invention is such that plasma with high density and high electron temperature (strong plasma state) and plasma with low density and low electron temperature (weak plasma state or plasma extinction state) can be generated periodically. Therefore, it is possible to easily obtain a high-density, high-electron plasma while keeping the temperature of the sample low. Furthermore, since the amount and type of generated ions and neutral radicals can be made different between the plasma generation state and the plasma extinction state, by changing the duty W during energy modulation, ions that contribute to the surface treatment of the sample can be made different. The ratio of ions to neutral radicals, ion species, and neutral radical capture can be controlled over a wide range.

As a result, it has become possible to provide a high-performance plasma process with a wide range of applications.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using figures.

FIG. 3 shows the basic configuration of a microwave plasma processing apparatus according to the present invention. In the figure, after a vacuum chamber consisting of a reaction chamber 1 and a discharge chamber 2 is evacuated to approximately 10 Torr by an exhaust system 14, a discharge gas G is pumped through a needle pulp 3 to a predetermined pressure (10-5 to 10 Torr). -IT
Orr) is introduced into the vacuum chamber. Microwaves having a frequency of 2.45 GH2 generated by a microwave oscillator 6 such as a magnetron propagate through a waveguide 7 and are introduced into a discharge tube 8 forming a discharge chamber 2 . This release
The chamber 8 is made of an insulating material such as quartz or alumina to allow microwaves to pass through. A power modulator 12 is connected between the microwave oscillator 6 and a power source 11 for driving the microwave oscillator 6.

A magnetic field is formed between the electromagnet 9 and the permanent magnet 10 in the discharge chamber 2 and a partial region of the reaction chamber. When a microwave electric field is supplied to the discharge chamber 2 by the microwave oscillator 6 in this state, a magnetic field microwave discharge is generated due to the mutual action of the magnetic field and the microwave electric field, and plasma is formed. Active ions and neutral radicals formed in this plasma reach the surface of the sample 4 placed on the sample stage 5, and etching is performed.

Now, the difference between this embodiment and the conventional example shown in FIG. 1 is that the microwave oscillator 6 and the driving power supply 11
This is the point where the power modulator 12 is inserted between the two. The power modulator 12 can be easily realized, for example, by controlling the emission current f of the microwave oscillator 6 using a triode vacuum tube. Additionally, it is possible to modulate or chop the microwave output. As a result, the release turtle room 2
A high-density, high-electron-temperature plasma and a low-density, low-electron-temperature plasma are periodically generated. If you change the expression,
When a strong plasma state and a weak plasma state (or plasma extinction state) appear periodically in the discharge chamber 2, K is obtained. By keeping the average value of the microwave power supplied to the discharge chamber 2, that is, the duty, constant, the temperature of the sample 4 can be kept constant. Obtainable. In high-density, high-electron-temperature plasma (strong plasma state), the amount of ions incident on the surface of the sample 4 can be made extremely large compared to the amount of neutral radicals. On the other hand, in a low-density, low-electron-temperature plasma (weak plasma state) or in a plasma extinction state, neutral radicals are the main particles incident on the surface of the sample 4 that contribute to surface treatment. Further, the ion species and neutral radical species generated in a high-density, high-electron-temperature plasma are different from those in a low-density, low-electron-temperature plasma.

Therefore, by changing the duty of power modulation and the output ratio between high output and low output, l) the ratio of ions to neutral radicals that contribute to surface treatment, ion species, and neutral radicals can be controlled over a wide range. It becomes possible to do so.

FIG. 4 shows the temporal change in the microwave power supplied to the discharge chamber 2 when the power modulator 12 modulates the power to the microwave oscillator 6. , , ,) and the lowest (Pffi+n) time are assumed to be τ1.τ2.

τ0=τ1+τ2 is the modulation period. P, 1! and ratio T
1/To has a mutual relationship based on the conditions for keeping the temperature of the sample 4 low, and I P, n, -- (400W t tτ0 is desirable. And τ1 is the residence time of ions in the plasma (=10- It is desirable that the reaction time is sufficiently longer than 5 sec) and sufficiently shorter than the residence time of the neutral radical in the reaction chamber 1 (=10-'5ea). That is, 10-5 Sec (r l (10-1 g (y2) is desirable).

Note that since τ2 has almost no sample (heating) externality and corresponds to the radiation cooling time, the sample can be kept at a low temperature without using any other water-cooling sample means.

τ! Depending on the ratio of and τ2, water cooling means may be required.

FIG. 5 shows the microwave RL waves supplied to the discharge chamber 2, -1. c.
This shows another means of modulating force.

A shutter 13 made of an electrically conductive material is provided in the middle of the waveguide R7 that propagates the microwave.

By mechanically opening and closing the shutter 13 as shown by the arrows, it is possible to modulate the microwave power passing through the noj% wave tube 7. Of course, it is desirable to capture the magnetron 6 using reflected waves using an inlater or the like.

The above description has been about plasma processing equipment that uses magnetic field microwave discharge, but other plasma processing equipment (such as those that use RF discharge) can also modulate the power (such as RF power) required to generate and maintain plasma. It goes without saying that the same effect can be obtained by adding it. Also, to change the type of discharge gas! Needless to say, it is possible to perform a nitrogen-etching action or a deposition action.

〔Effect of the invention〕

As described above, the present invention enables periodic generation of high density, high electron temperature plasma (strong plasma state) and low density, low electron temperature (weak plasma state) or plasma extinction state, thereby reducing duty. By suppressing the upper limit, it is possible to easily obtain plasma with high density and high electron temperature while keeping the temperature of the sample low. Therefore, it becomes possible to vary and control plasma parameters over a wide range. Furthermore, since the amount of ions and neutral radicals generated and these substances can be made different between the strong plasma state and the weak plasma state, by changing the duty during eorgic modulation, the ions that contribute to the surface treatment of the sample can be changed. It becomes possible to control the ratio of ions and neutral radicals, ion species, and neutral radical species over a wide range.

As a result, the present invention has made it possible to provide a plasma processing apparatus with high performance and a wide range of applications.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of a conventional plasma processing apparatus, Fig. 2 is an explanatory diagram of an etching cross-sectional shape, Fig. 3 is a basic configuration diagram of a plasma processing apparatus according to the present invention, and Fig. 4 is an example of modulation of microwave power. FIG. 5 is a partial configuration diagram of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction chamber, 2... Discharge chamber, 3... Needle valve, 4... Sample, body... Sample stage, 6... Microwave oscillator, 7... Waveguide, 8 ...Discharge tube, 9...
Semi-magnet, 10... Permanent magnet, 11... For microwave oscillator, Jellybeam source, 12... Modulator, 13... Shutter, 14... For exhaust, 12th 22nd ( a) <b) IF

Claims (1)

[Claims] 1.1 A gas introducing means for introducing a discharge gas into the empty chamber, a plasma forming means for forming a plasma of the discharge gas in the vacuum chamber, and an active particle in the plasma injected into the vacuum chamber. A sample stage on which a sample to be surface-treated is placed, and the amount of energy supplied to the plasma forming means so that the plasma periodically forms a strong plasma state, a weak plasma state, or a plasma extinction state. A plasma processing apparatus characterized by comprising: energy modulation means for modulating energy. 2. The plasma processing apparatus according to item 1, wherein the plasma forming means comprises means for applying a microelectric field and a magnetic field to the released gas introduced into the vacuum chamber. 3. The microwave electric field applying means comprises an oscillator that generates the microwave, a power source that drives the oscillator, and a waveguide that guides the generated microwave to the vacuum chamber, and the magnetic field applying means 2. The plasma processing apparatus according to item 2, wherein the f'Wt magnet is provided around the outer periphery of the vacuum chamber. 4. The plasma processing apparatus according to item 3, wherein the energy modulation means comprises an eight-frequency power converter provided between the power source and the oscillator. 5. The plasma processing apparatus according to item 3, wherein the energy modulation means comprises a shutter provided in the waveguide.